The present invention relates to a semiconductor light emitting device and a fabrication method thereof, and particularly to a semiconductor light emitting device used for a semiconductor laser or a light emitting diode using a nitride based compound semiconductor allowing light emission of violet light and a fabrication method thereof.
A semiconductor laser device allowing light emission of violet light has become a focus of attention as a light source for optical disk systems. As a semiconductor light emitting device using a nitride based compound semiconductor allowing light emission of violet light, there is known a gallium nitride based semiconductor laser device disclosed in Japanese Patent Laid-open No. Hei 11-214788. In this gallium nitride based semiconductor laser device, an active layer made from a nitride semiconductor held between at least cladding layers made from nitride semiconductors is provided on a substrate, wherein a current is injected in a stripe region (which is called a ridge) having a width narrower than that of the active layer. This laser device is characterized in that the ridge width is specified to be in a range of 0.2 to 1.8 xcexcm.
The above-described related art semiconductor laser device, however, is disadvantageous in that since the ridge width is in the range of 0.2 to 1.8 xcexcm, the current consumption becomes as large as 100 mA or more. For example, a semiconductor light emitting device used for a short wavelength digital video disk recording apparatus requires an output of about 30 mW, and to stably operate the semiconductor light emitting device, it is required to reduce the current consumption to 100 mA or less and also to reduce the power consumption.
An object of the present invention is to provide a semiconductor light emitting device stably operable with an output of about 30 mW by setting a threshold current to 100 mA or less and also setting a horizontal angle to 6xc2x0 or more, and to provide a fabrication method thereof.
To achieve the above object, there is provided a semiconductor light emitting device including: a cladding layer having a first conductive type, an active layer, and a semiconductor layer including at least a cladding layer and having a second conductive type reversed to the first conductive type, which layers are sequentially stacked on a substrate; wherein a ridge is formed on part of an upper portion of the semiconductor layer; each of the cladding layer having the first conductive type, the active layer, and the semiconductor layer having the second conductive type is made from a nitride based group III-V compound semiconductor; and the width of the ridge is in a range of 1.9 to 2.6 xcexcm.
As a result of experiments performed by the present inventor, it was found that, for the semiconductor light emitting device of present invention in which the ridge width is in the range of 1.9 to 2.6 xcexcm, the power consumption necessary for obtaining an output of 30 mW becomes about 0.6 W or less and the current consumption necessary for obtaining the output of 30 mW becomes about 100 mA or less, and for a semiconductor light emitting device in which the ridge width is narrower than 1.9 xcexcm or wider than 2.6 xcexcm, the current consumption becomes more than 100 mA and thereby the device becomes unusable, and also the power consumption becomes rapidly larger.
According to the semiconductor light emitting device of the present invention having the above-described configuration, since the ridge width is in the range of 1.9 to 2.6 xcexcm, it is possible to realize a semiconductor laser device allowing light emission of violet light, characterized in that an emission efficiency, expressed by a threshold current, is as low as 100 mA or less, and also to realize a semiconductor laser device allowing light emission of violet light, characterized in that a horizontal angle (a half-value of a far-field pattern in the horizontal direction) is 6.0xc2x0 or more.